testifier vs witness

testifier and witness both are nouns.

Word	Noun	Adjective	Verb	Adverb
testifier	Yes	No	No	No
witness	Yes	No	Yes	No

As nouns, witness is a hypernym of testifier; that is, witness is a word with a broader meaning than testifier:

Other hypernyms of testifier include informant, witnesser.

testifier (noun)	witness (noun)
a person who testifies or gives a deposition	testimony by word or deed to your religious faith
	someone who sees an event and reports what happened
	a close observer; someone who looks at something (such as an exhibition of some kind)
	(law) a person who attests to the genuineness of a document or signature by adding their own signature
	(law) a person who testifies under oath in a court of law

testifier (verb)	witness (verb)
	be a witness to
	perceive or be contemporaneous with